Genuine Volvo 940 Oxygen Sensor

Volvo 940 Oxygen Sensor Parts and Q&A

• Oxygen Sensor
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  Q: What is the function and operation of the Oxygen Sensor (02S) in vehicle exhaust systems on Volvo 940?

  A:

  The Oxygen Sensor (02S) produces an electrical voltage in response to oxygen content in exhaust gases, and is generally mounted in the exhaust manifold, and some models have internal heating for faster response. It gives a voltage between 0 and 1 volt, with lower voltages representing lean mixture and higher voltages representing rich mixture, with the ideal fuel to air ratio represented by voltages between 0.4 and 0.6 volts. Later models are equipped with two sensors for tracking the effectiveness of the catalytic converter, one tracking emissions before the converter and the other tracking emissions after the converter, giving the effectiveness of the reduction of emissions. The sensor has a specific temperature that it needs to work, and is in the OPEN LOOP mode until the engine has reached this ideal temperature, then it becomes CLOSED LOOP mode, so that the engine controller can control the air-fuel mixture depending on readings from the sensor. A Heated Oxygen Sensor (H02S) ensures optimal temperature for faster CLOSED LOOP operation where the engine controller uses information from the sensor to adjust the injector pulse width, while in OPEN LOOP the engine controller uses preprogrammed values. For testing, the H02S is disconnected and supply voltage to the heating element is checked, followed by resistance checks and continuity tests for proper function. Removing the battery by disconnecting the battery, jacking the vehicle up, carefully remove the sensor with suitable tooling, installing the sensor includes applying anti-seize compound and tightening to specified torque before reconnecting the wiring harness and lowering the vehicle.